Known friction clutches provide a releasable torsional connection between a motor vehicle engine flywheel and an associated transmission. Such clutches require adjustment of the clutch pressure plate's released position relative to the flywheel to ensure that complete engagement of the friction clutch can be achieved after the friction material of the clutch driven disc begins to wear. Some clutches are provided with automatic adjustment mechanisms which are disposed between the pressure plate and an associate biasing member such as a diaphragm spring. The clutch engagement force provided by the biasing member in the engaged condition prevents adjustment of the adjustment mechanism. However, when the clutch is released, excessive adjustment of the clutch may occur, particularly if the biasing member separates from the pressure plate. It is known to provide elements connected to the pressure plate which limits adjustment. However, adjusters which have such a limiting element typically also require complete disengagement of the biasing member from the pressure plate before adjustment occurs. This requirement of complete disengagement results in adjustment occurring only periodically, when the clutch pedal is fully depressed.
It is therefore desired to provide an adjustment limiting device which allows for continuous automatic adjustment with each clutch pedal stroke while preventing over adjustment for automatic adjustment mechanisms. It is further desired to provide a limiting device comprising a minimal number of parts.
Another concern is with the difficulty of resetting adjustment mechanisms. Some types of adjustment mechanisms may require disassembly of the pressure plate from the cover to reset the adjustment mechanism. When a worn driven disc is replaced, it is highly desirably to reset the adjustment mechanism to a new or unworn position from a worn position without disassembling the pressure plate from the cover.
It is desired to provide a clutch having an easy-to-use reset mechanism which enables the adjustment mechanism to reset the adjustment mechanism from a worn position to a new or unworn position.